Generally, a wind power generating device includes a base, a power generator, and a fan wheel connected to the power generator. The fan wheel receives and is pushed by intake wind current, so as to retrieve and convert wind energy in the wind current into mechanical energy. The power generator connected to the fan wheel receives and is therefore driven by the mechanical energy transmitted by the fan wheel to generate electric energy.
In the above-described conventional wind power generating device, the fan wheel is the only means that directly brings the power generator to generate electric power. And, in the power generator, only the windings or the magnetic bodies thereof are rotated without any other transmission gear. Therefore, the fan wheel rotates faster when the intake wind current is strong, and rotates slower when the intake wind current is weak. That is, the rotational speed of the fan wheel is affected by the strength of the intake wind current. As a result, the power generator could only have relatively small power generation capacity, and the whole wind power generating device fails to supply a large scale of power.